'He saved the higher education bill, much to my chagrin. And he's got a self-deprecating manner'

Did Alan Johnson mean to become the week's most talked-about politician? Opinions are divided, even among his friends, but after one breakfast interview on GMTV, the education secretary has gone from being a likely lad of the cabinet, one of a few candidates to take over from John Prescott as deputy prime minister, to being the frontrunner.

"There's no campaigning. But people have asked me if, when, there is a vacancy, if I'd be interested and I've said quite honestly: yes, I would," Mr Johnson told GMTV. He had, he reminded viewers, already been to Dorneywood - the grace-and-favour house Mr Prescott had to give up last week - when he was a postman, to deliver letters.

These comments were not dissimilar to his admission in an interview in the Mail on Sunday in April. "I am prepared to stand to be elected," he told Petronella Wyatt then, and said yes when he was asked whether he would get on with prime minister Brown.

If anything, Mr Johnson has done too well. He has become the newly anointed "Anyone but Brown" candidate. Peter Oborne, the rightwing columnist, wrote in the London Evening Standard this week that Mr Johnson was Labour's John Major, who had "risen without trace" with "no enemies and fewer accomplishments".

Friends say that is unfair. But like Mr Major - and Mr Prescott - a lot of his appeal is based in his background. Mr Johnson was orphaned at 12, and left Sloane grammar school in Chelsea, west London, at 15 with no O-levels. "My working-class credentials are impeccable, although I don't get them out and polish them every five minutes," he told the Guardian in 2003.

He likes football (QPR) and music (the Rolling Stones, the Yardbirds). He played guitar and made a demo. "I'm not like the prime minister jumping around in bloomer pants, or whatever it was. I was a serious music fan - still am."

His first job was at the Remington Electric Shaver company, and then he stacked shelves at a couple of supermarkets before becoming a postman. He made a quick rise up the slopes of the Union of Communication Workers and became its youngest general secretary in 1992, leading an accomplished campaign to force Michael Heseltine to abandon post office privatisation.

Mr Johnson was the only union leader to embrace Tony Blair's ditching of clause 4 and though he was prepared to criticise the new Labour leader, when he intervened in a postal strike, his value as a Blairite was understood. "When he was younger he was leftwing. But in the 1980s he'd be canvassing and people would be talking about crime on their estate, and then he'd go to meetings and members would be wanting to do something about Nicaragua," one friend said.

Mr Johnson was parachuted into the safe Labour seat of Hull West and Hessle, neighbouring Mr Prescott, just before the 1997 election, and has enjoyed a rapid ride up the ministerial ladder. He shared credit with the then education secretary, Charles Clarke, for pushing the top-up fees legislation through - "I was the charm and Charles was offensive" Mr Johnson jokes.

In 2004 he won his first cabinet job, at work and pensions, where in a year he scored some notable successes. He negotiated a reform of incapacity benefit and raised the alarm over women's pensions. At trade and industry he launched the review of nuclear policy, averted moves to a sell-off of the Royal Mail, and brokered the deal to safeguard a pension age of 60 for existing public sector workers. One official said he was very good at prioritising, and prepared to delegate.

Mr Johnson's style is to tackle the "guerrillas in the garden", issues where the department is in trouble. A Labour MP who has worked with him said: "He's capable of thinking out of the box. And he is capable of being reasonable."

He can be ruthless: he forced the resignation of the head of the Child Support Agency while they were on the way to a select committee. Early in his cabinet career, he was, friends say, prepared to remind both prime minister and chancellor of the agreed way forward, particularly on welfare reform. "He'd be friendly, but he'd stand up to both."

That is the characteristic which impresses friends and foes. Mr Johnson has a disarming style even when he is disagreeing with them."There's a touch of white van man about him," one MP said. "He's never lost his accent." He has never lost his ability to turn a good phrase, either. Earlier this week he defended shifting the focus in further education to skills. "More plumbing, less pilates; subsidised precision engineering, not oversubsidised flower arranging ... tai chi may be hugely valuable to people studying it, but it's of little value to the economy." Charles Clarke would have been slaughtered for much less. His performance last month at the dispatch box during the schools bill, managing a record Labour rebellion for a report stage, inspired awe. David Willetts, his Conservative shadow, said: "I cannot think of any member of the cabinet who could have handled the rebellion better than he did."

Phil Willis, the former Lib Dem education spokesman, put a bet on Mr Johnson getting to No 10 when he was higher education minister. "He wasn't even mentioned as a possibility. But history tells you that the heir apparent never inherits the throne. He is a brilliant negotiator. He saved the higher education bill, much to my chagrin. You always feel that you are being listened to. And he's got a self-deprecating manner which is all too rare in politics."

Mr Johnson's ambitions may yet be frustrated. He's relatively old at 56. And he's not a woman, which matters to many centrists who might otherwise support him. He is friendly with the chancellor but not close - before he became work and pensions secretary they had seldom crossed paths.

Were they to seriously fear him as a candidate for the leadership, Brownite outriders are prepared to gun him down. A friend casts him as a Blairite with leftish tendencies, like David Miliband, but the left may still turn on him. "Alan Johnson can do no wrong in my house," said the uber-Blairite junior schools minister, Lord Adonis, this week. With friends like that, he may get plenty of enemies. But right now, Alan Johnson is the man to watch.

The CV

Born Alan Arthur Johnson, May 17 1950 in London. His father deserted the family when Alan was eight and his mother died four years later. Brought up by his elder sister Linda in a council flat in Battersea

Family Married to Laura Jane Patient with one son; one son and two daughters (one deceased) from previous marriage

Education Sloane Grammar, Chelsea. He left at 15, without qualifications

Career Worked at Remington Electric Shaver company before becoming a shelf stacker at Tesco; 1968: became a postman in Slough. Dorneywood, the ministerial grace and favour house, was on his round; 1993: became leader of the CWU, the union's youngest general secretary; 1997: elected as MP for Hull West and Hessle; 2001: minister of state, Department of Trade and Industry, with responsibility for employment relations; 2003: minister of state for higher education, Department for Education and Skills. Given job of steering top-up fees legislation through Commons; 2004: appointed work and pensions secretary, becoming the first former union leader in 40 years to become a cabinet minister; 2005: trade and industry secretary; May 2006: appointed education and skills secretary

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